Vehicles incorporating electric motors require high voltage energy storage systems in order to properly power the motor. High voltage often requires that multiple battery cells be electrically connected together in series. Battery storage cells, when charging or discharging generate heat due to chemical reactions within the cells, as heat generation is a byproduct of electricity generation. When multiple battery cells are contained in close proximity, the heat generated in each cell can become multiplicative throughout the system and can cause problems such as cell thermal runaway which can destroy the storage system. Additionally, for optimal energy efficiency, uniform temperature of the battery cells must be maintained. Thus it is necessary and advantageous for such systems to include a means to cool the battery cells.
Additional problems with high voltage battery cells are risks of corona or arc flash if an open circuit occurs or fires from ignition of vented gases. Further, salt fog and foreign particles can cause corrosion and unwanted electrical leakage current paths or short circuits to exist in the storage system.
Current designs use air cooling or liquid cooling built with manifolds and piping to remove excessive heat from the battery cells. Air cooling does not prevent salt fog or other corrosive materials from reaching the battery cells, even when a filter is used. Liquid cooling built with manifolds and piping may leak and cause leakage current paths to exist in the storage system. Additionally, these designs add volume to the storage system which causes problems with space-efficient original designs or hybrid retrofit applications.
Other designs incorporate a non-conductive fluid inside a casing that contains the battery cells. In some cases, the fluid may be made to move within the casing which increases heat energy transfer. These designs may reduce problems with arc flash, corona, and corrosion. However, these designs are difficult to service as the fluid must be drained or otherwise contained when servicing the battery cells or other components. Further, these designs still may not provide adequate heat energy transfer in order to avoid cell thermal runaway.
Thus, there is a need for improvement in this field.